Japanese Utility Model Publication Number Sho 51-146490 (Japanese Utility Model Application Number Sho 50-66966) discloses a conventional coolant-supplying device as shown in FIG. 19. The conventional coolant-supplying device includes an air nozzle E which blows air A to a position that is upstream (relative to the rotation of the grinding wheel) from a position where a coolant C sprayed from a coolant nozzle CN contacts a grinding wheel G. As a result, the rotation of an air layer following the circumferential surface of the grinding wheel is obstructed, and the air flow does not reach the grinding point. Thus, the coolant C can be effectively supplied to the grinding point.
However, in this conventional coolant-supplying device, air A is blown against the circumferential surface of the grinding wheel G in a direction that is opposite to the direction of rotation of the grinding wheel G. Thus, air flow dragged by the circumference of the grinding wheel opposes the flow from the air nozzle E, which results in turbulence. The turbulence impedes the supply of coolant to the grinding point.
Japanese Utility Model Number Hei 2-100770 (Japanese Utility Model Application Number Hei 1-7603) discloses a grinding wheel cleaning device for a conventional grinder as shown in FIG. 20. This grinding wheel cleaning device includes a grinding wheel washing device GC disposed inward from a coolant nozzle CN of a coolant spraying device so that the grinding wheel washing device GC is positioned close to the grinding wheel G. The cleaning nozzle GCN is a pipe with an opening at the end formed from applying pressure to compress it into the shape of a tongue. The cleaning nozzle GCN applies a uniform spray horizontally across the entire width of the grinding surface of the grinding wheel G to remove grinding chips that adhere to and clog the pores of the grinding surface. Thus, the grinding surface is maintained in a proper state.
However, the object of a grinding wheel cleaning device is different from that of the present invention. Moreover, the spray that blows away debris from the grinding surface of the grinding wheel G obstructs the coolant supply to the grinding point.
Japanese Laid-Open Patent Publication Number Hei 6-8143 discloses a conventional coolant fluid supplying device as shown in FIG. 21. The conventional coolant fluid supplying device includes a fairing P with a wing-shaped cross-section positioned close to the grinding point on a circumferential surface GO of the grinding wheel G. The fairing P is supported at an appropriate distance from the grinding wheel G and at an angle that is based on the diameter of the grinding wheel G. The fairing P regulates the flow of the air layer generated near the circumferential surface GO when the grinding wheel G is rotated at high speeds. When supplying coolant fluid between the fairing P and the grinding wheel G, a large amount of the coolant fluid can be guided to the grinding point.
However, in this conventional coolant fluid supplying device, the coolant fluid cannot be reliably guided to the grinding point at the surface of the grinding wheel G since the air flow in the air layer, which is regulated by the fairing P, is present at the grinding point.
A conventional coolant supply device used in ultra high speed machining as shown in FIG. 22 is disclosed in Japanese Laid-Open Patent Publication Number 6-155300. The conventional coolant supply device provides coolant which is sprayed at a high pressure from a first nozzle N to a grinding point K. An air film forms on the circumferential surface of the grinding wheel G. A stopping plate SP disposed above the grinding point K prevents the air film from reaching the grinding point K.
However, in this conventional coolant supply device for ultra high speed machining, a gap is formed between the stopping plate SP and the circumferential surface of the grinding wheel G, and this gap prevents the stopping plate SP from completely preventing the air film from reaching the grinding point K. Therefore, it is necessary to spray coolant at a high spray pressure, which does not allow a low volume of coolant flow to be guided to the grinding point.